Multi-site trunked communication systems are known. A typical system includes communication units, communication sites, communication resources, and a communication resources allocator or manager. Generally, the communication sites are geographically dispersed throughout the system, such that each site has a substantially distinct coverage area. A number of communication resources are assigned to each site. At least one communication resource per site is used as a control channel, while the remaining communication resources are used as voice and/or data channels. Base stations or repeaters are used to support the communication resources and are located at each site. The communication resources may be telephone connections, time division multiplexed (TDM) time slots, carrier frequencies, and/or frequency pairs. These resources are managed by the resource allocator, which is also referred to as a central controller.
The communication units, also called subscribers, can be arranged in talk groups and may be located anywhere within the coverage area of the system, i.e., the cumulative coverage area of all the sites within the system. A subscriber from a talk group may request a group call which allows all members of the same talk group that are located within the system to communicate with each other. The subscriber initiates this request for a group call by transmitting, via the control channel of the site with which it is associated, notification to the central controller. The central controller maintains a database of the subscribers within the system, the sites with which they are associated, and their membership within the talk group, among other information. Thus, the central controller is able to service the request for a group call by allocating communication resources at the various sites with which various members of the talk group are associated, so as to permit communications among members of the talk group. Generally, the information stored in the database of the central controller is maintained through communications between the central controller and each subscriber. As a subscriber travels throughout the coverage area of the system, so as to change its associated site, the subscriber communicates updated site association information to the central controller so that the central controller can maintain its database.
A problem arises when there is a failure or initialization at the central controller, and its database becomes obsolete or unusable. For example, if a central controller has an appreciable amount of down time, subscribers may change site affiliation, thus making at least some portions of the database obsolete. Generally, the central controller does not know which subscribers have changed affiliation, and thus must query all subscribers to get information needed to update the database. Similarly, if the information in the database is lost, the central controller must communicate with each subscriber to rebuild its database. This process can take a substantial amount of time during which the radio communication system is not fully operational.
It is desirable to have a radio communication system, such as a multi-site trunked system, which operates with minimum down time despite failures in any particular portion of the system. In a typical multi-site trunked system of the prior art, a central controller failure could result in significant down time. Therefore, an improved management approach is needed.